--- a/numerics/interpolation.py	Fri Feb 27 13:34:05 2015 -0800
+++ b/numerics/interpolation.py	Sat Feb 28 13:51:40 2015 -0800
@@ -1,10 +1,10 @@
 #!/usr/bin/env python
 
-
 """
 interpolation
 """
 
+# imports
 import argparse
 import sys
 
@@ -58,8 +58,9 @@
     nearest_neighbors = neighbors(points, x)
 
     # we don't support endpoints yet; this is interpolation, not extrapolation
-    assert not any([(neighbor[0] is None or neighbor[1] is None)
-                    for neighbor in nearest_neighbors])
+    if any([(neighbor[0] is None or neighbor[1] is None)
+            for neighbor in nearest_neighbors]):
+        raise AssertionError("Bad neighbors: {}".format(nearest_neighbors))
 
     retval = []
     for index, (left, right) in enumerate(nearest_neighbors):